In magnetic tape cartridges, which are being used as storage media that are employed in external storage units for computers, etc., there is known a type where a single reel with magnetic tape wound thereon is rotatably housed within a cartridge case. This magnetic tape is employed to archive data for computers, etc. Since important information has been stored, the magnetic cartridge is constructed so that problems, such as tape jamming, etc., do not occur and that the magnetic tape is not pulled out of the cartridge case unexpectedly.
In addition, a leader member such as a leader pin is rigidly attached to the leading end of the magnetic tape, and a drive unit is constructed so that the leader pin is pulled out at a recording-reproducing unit to forward or rewind the magnetic tape. The leader member is pulled in and out of the cartridge case through an opening formed in the cartridge case. In the opening, it is preferable to make the case wall thin and form an insertion-guide portion for leading in and guiding the end portion of the leader member so that the pulling-in-and-out of the leader member can be easily performed.
Hence, the aforementioned magnetic tape cartridge has the disadvantage that the insertion-guide portion will be deformed and damaged by shock produced due to dropping of the magnetic tape cartridge.
More specifically, as illustrated in FIG. 35, an opening 10 in a generally rectangular cartridge case 4, for pulling in and out a leader member (or a leader pin) 5 rigidly attached to the leading end of magnetic tape, is formed in the side surface, near corner portions 4a, of the case 4. The top and bottom wall surfaces inside the opening 10 are provided with housing recesses 20 in which the upper and lower ends of the leader member 5 are inserted and retained. Insertion-guide portions 21 are provided from the housing portions 20 to the open end so that the upper and lower ends of the leader member 5 are guided when they are housed. The insertion-guide portions 21 that are thin are positioned near the case corner portions 4a. Because of this, if the cartridge case 4 falls with the corner portions 4a downward, that is, if a falling shock is exerted directly on the corner portions 4a, the shock wave will propagate from the corner portions 4a to the top and bottom wall surfaces of the opening 10 and therefore the insertion-guide portions 21 with reduced strength will be buckled under pressure and the exterior surface will become bulged, as shown by broken lines. Because of this, the cartridge case 4 has the following problems: it becomes impossible to load it into the drive unit; it becomes impossible for the insertion-guide portions 21 to guide the upper and lower ends of the leader member 5; and the leader member 5 cannot be pulled in and out properly and thus it becomes impossible to use the cartridge case.
In addition, since the leader member 5 is pulled out from the opening 10 by being engaged by a taking-out mechanism provided on the drive side, in the case interior region near the opening 10 it is difficult to dispose a member, for fastening the upper and lower cases 2 and 3 together by small screws, in the vicinity of the corner portion 4a near the opening 4, in order to avoid interference with the taking-out mechanism and assure a running region for magnetic tape 6. For this reason, rigidity near the opening 10 is reduced, so the cartridge case is disadvantageous for enhancing strength to counter the aforementioned falling shock.
The present invention has been made in view of the points mentioned above. Accordingly, it is a first object of the present invention to provide a magnetic tape cartridge that is capable of preventing an insertion-guide portion provided in an opening from being deformed due to shock produced by a fall, etc., to assure reliability.
Magnetic tape cartridges, incidentally, are primarily employed to back up data stored in memory for computers. These magnetic tape cartridges are grouped, for example, into two types. One type is constructed so that when the cartridge is not used, magnetic tape is completely wound on a reel and the leading end portion of the magnetic tape is retained in a leader block which is housed to cover a tape leader opening formed in one corner of a cartridge case. Another type is constructed so that in a tape leader opening formed in one side wall of a cartridge case, a lid openable and closable in a cartridge plane direction is urged toward a closing position by a spring and is retained in the closing position by a lid lock urged to a locking position by the spring so that it is not rotated when the cartridge is not used. The leading end portion of magnetic tape is retained by a hook assembled into the tape leader opening.
If a magnetic tape cartridge with such a construction is set in the recording-reproducing unit of a corresponding external storage unit, the engaging teeth of the reel exposed at the central portion of the lower case is engaged by the rotation means provided on the unit side. Then, in the case of the former, the leader block, as it is, is pulled out together with the magnetic tape by a tape pulling-out mechanism on the unit side, while in the latter the lid is opened by the tape pulling-out mechanism on the unit side and then the hook is pulled but together with the magnetic tape. Next, the magnetic tape is pulled in and to a predetermined position in a tape running path. In this manner, writing or reading of data with respect to the magnetic tape becomes possible.
Of the magnetic tape cartridges of the two kinds mentioned above, the former employing the leader block has the advantage that the tape pulling-out mechanism on the unit side is structurally simple, because the magnetic tape is pulled out only by holding and pulling out the leader block. However, the former has the disadvantage that dust tends to enter the cartridge interior through a gap between the tape leader opening and the leader block when the cartridge is not being used.
On the other hand, the closable lid type of the latter solves the problem of dust tending to enter the cartridge interior, but has the problem that the tape pulling-out mechanism on the unit side becomes complicated and space for the rotary lid is required, because when pulling out the tape, the lid lock is first unlocked and then the lid must be opened. The latter also has the problem that on the cartridge side, the step of assembling a torsion spring for urging the lid and a coil spring for urging the lid lock is required when assembling the cartridge.
Hence, there has been proposed a magnetic tape cartridge in which a slide door is provided for opening and closing the tape leader opening and a spring member for urging this slide door toward a closing position is disposed in a passageway along which the slide moves. In this type of magnetic tape cartridge, a cartridge case is constructed by joining upper and lower cases together. In a side wall of the cartridge case, a tape leader opening is formed between the upper and lower cases and in close proximity to a corner of the cartridge case. A slide door is provided inside the surface of the cartridge case in order to prevent it from being damaged when shock is exerted on the slide door, for example, by dropping of the cartridge case. Therefore, the passageway along which the slide door moves is provided inside the exterior wall on the side of the tape leader opening.
However, since a generally circular interior wall (rib) is provided around a single reel with magnetic tape that is rotatably housed within the cartridge case, an exterior wall 234 on the side of the tape leader opening and the aforementioned interior wall 235 rise from the bottom wall 236 of the lower case 201b, independently of each other, and in opposition to each other across the moving passageway 237 for the slide door, as shown in FIG. 27A which is a sectional view of the lower case 201b. The upper case also has the same construction. For this reason, if the upper and lower cases of the cartridge case are manufactured by injection molding, resin pressure will be less likely to be transmitted to the part of the exterior wall 234. Because of this, there arises a problem that the exterior wall 34 will tilt inside, as shown in FIG. 27B. If the exterior wall 234 tilts inside, the moving passageway 237 for the slide door will be narrowed, and the operation of opening and closing the slide door will be obstructed because a proper gap with the slide door is not formed. In addition, the outside dimensions of the cartridge are reduced. This will cause malfunction within the recording-reproducing unit.
In view of the aforementioned circumstances, a second object of the present invention is to prevent the aforementioned tilt of the exterior wall, in a magnetic tape cartridge provided with a slide door which opens and closes a tape leader opening for pulling out an end of magnetic tape.
This type of magnetic tape cartridge is also equipped with a plastic cartridge case, constructed by joining a generally square flat upper case and a generally square flat lower case at their four corners by a joining means such as small screws.
FIG. 36 is a plan view showing the vicinity of a tape leader opening in the lower case of such a cartridge case.
In FIG. 36, a tape leader opening 326 is formed in the end portion of the side wall 303a of a lower case 303. The top surface of the bottom wall of the lower case 303 has a recess 328 facing the tape leader opening 326. In the recess 328, a leader member (not shown) clamping the leading end of magnetic tape 320 is detachably retained, for example, by a retaining member consisting of a spring plate. Reference character L1 denotes a boundary line, on the maximum tape winding diameter side, of a tape running region; reference character L2 denotes a boundary line, on the minimum tape winding diameter side, of the tape running region. An arcuate rib 332 is erected outside of a reel 304 with magnetic tape 302 wound thereon. In the vicinity of the tape leader opening 326, a boss 334, equipped with a positioning hole (blind hole) 333 which is employed for positioning the magnetic tape cartridge with respect to a recording-reproducing unit when loading the cartridge into the unit, and a boss 336, equipped with a screw inserting hole (through hole) 335 for fastening the upper and lower shells, are erected close to each other.
In a one-reel type magnetic tape cartridge, unlike a two-reel type magnetic tape cartridge, a direction in which the magnetic tape 320 is pulled out is usually in an A-direction or B-direction, shown in the lower right of FIG. 36 (in the two-reel type, a C-direction). Because of this, on the maximum tape winding diameter side of the tape running region, the magnetic tape 320 runs close to the side wall 303b of the cartridge case and therefore there arises a problem that the magnetic tape 320 will tend to be attached to the side wall 303b of the plastic magnetic cartridge case in which static electricity is liable to occur. In addition, during archiving of the magnetic tape 320, it also tends to be attached to the side wall 303b, because it is wound on the reel and archived.
Therefore, there arises an inconvenience that during running, (1) the magnetic tape 320 will make contact with the side wall 303b and will be damaged, (2) data stored on the tape will be destroyed, and (3) recording and reproducing of the data will become impossible. In addition, since the magnetic tape 320 scrapes the wall surface of the side wall 303b, powder develops and causes the tape to be dropped out. Furthermore, there is also a fear that during archiving, a component coated on the magnetic tape will react with the resin component of the cartridge case and the magnetic tape 320 will be attached to the wall surface of the side wall 303b. 
Furthermore, since a compact and large-capacity one-reel type magnetic tape cartridge has recently been developed for backing up data, the tape wound body (wound ball) being housed within the cartridge case is close to the interior wall surface of the cartridge case, and the magnetic tape of the large-capacity type is low in rigidity because the thickness is as thin as a few μm. Because of this, the magnetic tape tends to be affected by static electricity.
In view of such circumstances, it is a third object of the present invention to run magnetic tape stably by preventing the attachment of magnetic tape onto the interior surface of the cartridge case to avoid the occurrence of the disadvantages mentioned above.